Support the bag from underneath, always
A bagged fish is a small volume of water with a living animal suspended in it, and it should be handled like a bowl of water, not a parcel. Slide both hands underneath and cup the bottom so the weight spreads across your palms, keeping the bag upright and the water still. Carrying a bag by its knotted neck is the classic mistake: the knot was tied for sealing, not for lifting, and a bag dangling from it swings with every step, sloshing the fish against the plastic, bending the water column, and sometimes working the knot loose entirely. If you must move several bags, move them in a box, one trip, both hands — never hooked over fingers by their necks.
Darkness and stillness do the calming
More journeys go wrong through light and motion than through time. A fish in a clear bag on a bright shop counter can see every looming hand and passing shadow, and each one reads as a predator. Set the bag down inside a dark box or an opaque carrier as soon as it is handed to you, and keep it there: darkness settles fish faster than almost anything else you can do for them. Walk smoothly, avoid stairs taken at a run, and do not set the box down and pick it up repeatedly. In the car, wedge the box on the floor behind a seat where it cannot slide, tip, or be sat beside a thumping speaker.
Temperature: carry the bag like it is already home
The water in a bag takes on the temperature of its surroundings within the hour, so treat the journey as climate control. An insulated box or a cool bag buffers the change; in summer, never leave the box in a parked car or a hot boot while you run other errands, and in winter, keep it inside the heated cabin and out of cold draughts. Do not float errands around the fish — the bag is the last thing you collect and the first thing you deal with at home. If a trip will run long, ask for the bag to be packed with a little extra water and plenty of air space, and for delicate fish, ask whether a second bag outside the first is worthwhile insurance against a leak.
Short trips, direct routes, gentle arrivals
Plan the route before the bag is tied: straight home, no detours, and the receiving tank ready before you leave — lights dimmed, a net and a jug at hand. At home, set the box down beside the tank and open it in low light. The carrying rules still apply in these last metres, because a bag swung out of a box and dropped into a bright tank undoes the care of the whole drive. Carry the bag two-handed to the tank rim, rest it there supported while you open it, and let acclimatisation happen at the fish's pace rather than yours.
Handing a fish over to someone else
Everything above matters twice when the fish is travelling to a new keeper, because the person at the other end cannot see how the fish was handled or what water it grew up in. Tell them the journey it has had, the temperature it travelled at, and anything about its feeding or behaviour they would otherwise learn the hard way. Those details belong on the fish's KinsLe Pet Passport, the packet that travels with the fish to every new home and handoff, so the receiving keeper can match conditions without guesswork.